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Comment by mcsoft | Hacker News Reader

It strikes me how a seemingly insignificant decision at the time - to position fuselage slightly higher above the ground - gave Airbus a strategic advantage 50 years later. It forced the competitor into a services of unexplainable and reckless decisions that break basic principles of reliable engineering. Which in turn led to a very visible disastrous business consequences: Boeing had to silently reduce 737 MAX production despite having secured orders for over 5000 planes. A case to be studied in business schools.

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Had Boeing built the 737 at the time Airbus built the A320 they would've had a taller undercarriage also. For example the narrow body 757 built around the time of the A320 does have this.

When the 737 was built back in the 60s it was intended to be a small regional jet, not the continent and ocean crossing aircraft it evolved into over the years since. It originally came with a retractable staircase for passengers to embark/alight the aircraft, and having a low fuselage also made it possible to hand load the luggage in a time before widespread belt loaders.

Why would they not have gone with a, say, 757 MAX - it seems to fit the bill spec wise. Is it that global pilot pool is not as great for the 757 as 737?

I don't think it matters how big the global pilot pool is for 737s. What matters to a specific airline is how many of their pilots are type rated for a particular aircraft. An airline that has standardized on the 737 is going to have a pool made up of mostly 737 rated pilots.

The 757 "max" is a 767. 757s and 767s share a common type rating.

It's not so much that the pilot pool is lacking, it's that a lot of airlines have a pool of existing 737 pilots already on their payroll. If you need to lay off half your employees, and replace them with an entire new pool of people, half of them are going to be terrible employees, and it will take you years to weed out the bad ones. For better or worse, pilot unions tend to be very strong. Firing them is difficult.

The 737 MAX wasn't beset by technical problems, they were social and political ones.

Huh? There's no such thing as a "737 pilot", there is a "pilot with 737 type rating". It's the whole "becoming a pilot in the first place" part that's hard, not certifying a new type. Plenty of pilots are certified to fly multiple types. The fundamentals of flight are the same across all planes.

The airlines would've just had to retrain their existing pilots to fly the new type. It's not nothing, but it's a lot less worse than massive lay-offs and rehiring.

I think you're severely underestimating the time, effort, and money involved in retraining into a new type rating. Usually the process is that the pilot takes a job running air-freight in their new desired type rating. There isn't any money in that, either for the pilot or the airline. You're correct that the fundamentals are the same, but the regulatory burden is enormous.

If getting a new type rating was cheap, this whole 737 max debacle never would have happened. Boeing would have just told everyone the 737 line was done, and to retrain into 767s or 787s, and for anyone who wanted to stick with the 737 to pound sand.

If it was cheap and/or easy for Boeing to tell airlines and/or pilots to get a new type rating, they gladly would have sold them 767s which do everything the 737 MAX does. (it does) They've probably already told them that and they've said no. And Boeing made the 737 MAX with the same type rating as the regular 737. Which is why we're here.

If I understand correctly, if you wanted to switch from 737s to 757s, you don't lay off your pilots and hire new ones. You take a few pilots at a time off of 737s, and spend months re-training and certifying them for 757s.

Correct. For example, Southwest Airlines _only_ operates 737's[0] so they would need to hire or retrain pilots if they brought any 757's. With the 737 Max they could get longer range and better efficiency with minimal additional training.

[0] https://en.wikipedia.org/wiki/Southwest_Airlines_fleet

I’m not an expert, but the 757 was a larger and heavier plane which changes the economics a lot. It also stopped production over a decade ago so restarting production would’ve been a challenge. On top of that as you said airlines wanted to maintain the 737 type rating so pilots didn’t need retraining.

The 797/NMA program Boeing is proposing is a replacement for the aging 757 and 767 fleets.

The 757 is a larger jet. Smaller jets have become increasingly popular with airlines. Probably had to do with the flexibility and extra timing / route options to offer by flying lots of small planes vs fewer large planes.

Also, global pilot pool doesn’t matter as much as what individual aurlines’ pilots are certified on. The specific airlines that operate 737s would prefer not to have to retrain their pilots on a new aircraft; if they had to retrain them for the 757max that would open the door to consider the airbus as an equally good option.

You mean genetic algorithms at work?

basic principles? i think that’s a bit far. the plane isn’t inherently unstable is it? i thought it’s just the black box of MCAS that is the problem and MCAS is there to avoid a lengthy type certification. it’s completely explainable.

and it wasn’t seemingly insignificant. it was for fuel efficiency. it was significant and they knew what they were doing.

They had to install MCAS because the plane was unstable in high AoA mode, i.e. during takeoff.

And it was unstable because larger CFM engines could not fit under the wing anymore so they had to put it further forward and a bit up. This increased the pitch up moment when a full power is applied.

Also, can't really see how the height of the fuselage above the ground affects fuel efficiency.

"Also, can't really see how the height of the fuselage above the ground affects fuel efficiency."

It doesn't. They wanted to use a larger, more fuel-efficient engine but the 737's ground clearance couldn't accomodate it. So they moved the engine forward.

> They had to install MCAS because the plane was unstable in high AoA mode, i.e. during takeoff.

Forgive me if I'm missing something, but isn't MCAS disabled while the flaps are extended, which is the case during takeoff and landing?

Yup. The real danger was during climb I believe. And it wasn’t unstable, just had a backwards feel at high angle of attacks which could lead to pilots inadvertently stalling it.

You are right though pilots prefer to retract flaps soon after liftoff since extended flaps mean more drag and less efficiency. And the danger comes from the low altitude thus no margin for error.

In the doomed ET302 flight they retracted flaps 62 seconds after liftoff at only about 1200ft above the ground. MCAS kicked in 5 seconds later. Had autopilot been engaged it'd also had saved them from MCAS trim down commands.

Seems to me that redundancy in mission critical systems where failure means loss of several hundred lives is a basic engineering principle. MCAS apparently relied on a single AOA sensor's input. The system had no way to validate the data or handle a mismatch, and the only recourse was to light up an (optional) disagreement indicator - but still relied on just the one sensor to apply control forces.

Well, yes: the plane is inherently unstable. That's why the MCAS system is there. The system itself is mostly fine, it does what it's intended to under ordinary conditions. The problem was that Boeing, in order to avoid costs to the buyer, declared that pilots did not require training on it and made the instrumentation that manages the system woefully inadequate to the task of handling malfunctions (plus the system relying on a single sensor is pretty brittle but adequate malfunction handling instruments would've mitigated that).

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